This invention relates to a safety device for a jug blender that has a blender jug adapted for seating engagement with a base equipped with an electric drive motor, said safety device having actuating members inside the base as well as a safety switch actuated by said actuating members and arranged in series in a power supply line of the drive motor so that the actuating members can only close the safety switch to supply the drive motor if the blender jug is correctly mounted.
A safety device of this type is known from U.S. Pat. No. 5,779,358, for example. In this known safety device a safety switch arranged in a power supply line for a drive motor mounted in the interior of the base support is only actuated by a collar covering the lower edge of the blender jug when the blender jug is correctly mounted on the base support, which in the known case means being correctly screwed on. In this arrangement the safety switch is positioned in the base support such that it can only be actuated by the edge of the blender jug collar and accidental actuation is possible only with difficulty. Blender jugs of this type with a thread at their edge are advantageous as regards the stable connection of the blender jug with the base formed by the threaded connection. A disadvantage is the rather awkward screwing of the blender jug on and off the base, which sometimes, when the turns of thread are gummed up with blended material, may only be possible by applying high force. To eliminate this problem there have already been proposals of jug blenders in which the blender jug is connected to the base as a push-fit, in which case care must be equally taken to ensure that the safety device for supplying power to the motor can only be actuated when the blender jug has been push-fitted onto the base in the proper position.
It is therefore an object of the present invention to provide a safety device for a jug blender that reliably prevents the dangerous cutter blades from being driven by the drive motor when the blender jug has not been push-fitted onto the base at all or correctly.
In accordance with an essential aspect the safety device of the invention works by the principle that the actuating members for actuating the safety switch can be actuated separately but in unison by two actuating points arranged in spaced relation to each other on the lower edge of the blender jug, in such manner that the safety switch can only be closed when both actuating members are actuated simultaneously and evenly by the two actuating points of the blender jug, i.e., when it is properly assembled.
The application described herein concerns a jug blender that is normally operated in a horizontal working position, hence the positional terms xe2x80x9chorizontalxe2x80x9d, xe2x80x9cverticalxe2x80x9d, xe2x80x9cperpendicularxe2x80x9d, xe2x80x9cradialxe2x80x9d and xe2x80x9caxialxe2x80x9d refer to the working position of the jug blender. It should be noted, however, that the safety device of the invention is sure to function in other working positions as well.
To achieve a constructional advantageous and safe solution the rocking lever is arranged for both pivotal and axial sliding motion. This ensures that the blender jug is correctly assembled only when the rocking lever is displaced horizontally, meaning that it is evenly pressed downwardly by the engagement surface of the blender jug. Only then can the appliance be switched on via the rocking switch.
The features of having the rocking lever be symmetrically shaped in longitudinal direction and having, in its center, a guide pin perpendicular to the plane of motion of the rocking lever, and the guide part having a vertical guide slot which extends parallel to the plane of motion of the rocking lever and in which the guide pin is guided with clearance result in a simple switch solution affording ease of turning and sliding. This applies equally to the features of having the rocking lever have, in its center, two mutually aligned guide pins, and the guide part having two parallel vertical walls in which two mutually aligned guide slots are provided for guiding the two guide pins.
According to the features of one embodiment, the actuating members include an elongate, normally horizontally extending rocking lever made of an insulating material whose length is adapted to the distance between the actuating points of the blender jug, said rocking lever being actuatable at each of its two ends by a respective actuating pin movable vertically within a bore in the upper wall of the base by pressure from the actuating points of the mounted blender jug, causing the lever to execute a rocking motion within a predetermined angle in the vertical plane combined with a sliding motion by a predetermined distance in vertical direction, and being for this purpose centrally guided in a guide part fastened in the base while being at the same time elastically biased in horizontal position toward the blender jug by a spring element, and the safety switch has an electrically conducting contact strip that is movable with the rocking lever, is fixed centrally to the lever bottom side facing away from the actuating pins, and projects in longitudinal direction of the rocking lever, said contact strip having a contact at each end, as well as two individual fixed contacts fastened to the base at a location opposite the contacts of the contact strip, so that the contacts of the movable contact strip can only be closed with the fixed contacts and power be supplied to the drive motor when the blender jug is seated in its proper relationship upon the base, causing, as this occurs, the actuating points of the blender jug to urge simultaneously and evenly both actuating pins, the rocking lever and the connected movable contact strip against the biasing force of the spring element horizontally downwardly into engagement with the two fixed contacts of the safety switch, at least in the end phase of the downward motion. An easy moving switch with a high level of safety and convenience is thus created with this solution.
The bilateral contact strip fastened to the bottom side of the rocking lever movable in a vertical plane thus ensures that the safety switch for supplying power to the drive motor can only be closed when the rocking lever is urged down evenly and horizontally, at least in the end phase of the downward movement, by the actuating points on the bottom edge of the blender jug. Only when this condition is satisfied is the drive motor supplied with power via the safety switch and the main switch serially connected therewith.
If anyone incorrectly actuates only one of the actuating pins and hence presses the rocking lever downwardly at an angle, the power circuit remains open and the drive motor cannot be started.
The features of having the spring element be a respective helical spring exposed to pressure and of identical spring force, which is seated in a vertical position symmetrically to the center of the rocking lever between a horizontal bottom of the guide part and an opposite end portion of the rocking lever, having the actuating pins be rigidly connected by an elongate arm placed down onto the rocking lever, and having the contact strip be of a resilient configuration at its two legs of identical length extending from the strip""s central fastening point, the legs being angled downwardly somewhat in uniform fashion in the direction of the fixed contacts lend the safety device a high degree of safety on account of its stable, nonsticking and amply dimensioned configuration.
The features of having the lower edge section of the blender jug have radially and axially projecting shoulders acting as the actuating points and adapted in form and position to the position of the actuating pins, and the upper part of the base having a mount encompassing the lower edge section of the blender jug by positive engagement therewith, the mount having recesses for accommodating the projecting shoulders by positive engagement therewith, whereupon the actuating pins extend upwardly through the bores within the recesses, and the features of having the blender jug have three projecting shoulders and the base have three mating recesses enable the blender jug to be seated on the appliance base with ease, but at the same time all parts still remain fully functional if, under exceptional circumstances, the outer parts of the safety device become dirty on the outside.
The above-mentioned and further advantageous features of the invention will become further apparent from the subsequent description of a preferred embodiment of the safety device of the present invention when reading this description with reference to the accompanying drawings.